Mindfulness

Does it work?

This summary is based on systematic reviews published in the last five years (since 2012) and subsequently published randomized controlled trials (RCTs). These publications indicate fast growing research efforts considering that the first RCT on the use of MBSR/MBCT in oncology dates from 2000. Details of the included studies are presented in table 1 for the systematic reviews and table 2 for the controlled clinical trials

Systematic reviews and meta-analyses

One overview of systematic reviews on mindfulness-based interventions in healthcare in general including six systematic reviews on cancer, 31 and seven systematic reviews 32-37 are available.

Four systematic reviews evaluate MBSR/MBCT in breast cancer patients and three in patients with various cancer diagnoses. There is some overlap in the systematic reviews in terms of the 39 individual RCTs, 6 non-randomized controlled trials, and 24 uncontrolled trials included (see table 1). The systematic review of systematic reviews by Gotink includes the systematic reviews by Piet et al 35 and Cramer et al 33.

The effect of mindfulness-based stress reduction (MBSR) has most commonly been investigated in female breast cancer patients. While most reviews would also have included mindfulness-based cognitive therapy (MBCT), no studies specifically on this intervention were located.

A common critique of these meta-analyses and systematic reviews is the lack of comparisons with other group-based psychosocial interventions not allowing for the identification of effects specifically attributed to specific mindfulness components rather than the attention and peer support associated with participation in psychosocial group based interventions 35. In addition the focus of most reviews on breast cancer patients and thus limits the generalization of the results of these studies towards the global cancer patient population.

All systematic reviews on breast cancer mentioned methodological shortcomings of the included studies. Methodological shortcomings of the reviews themselves further limit the conclusions of the reviews. These include small numbers of included trials 32-34, inadequate methodology for meta-analysis (ie, the use of mean differences for analyses of different outcome measures) 32, and lack of safety assessment in all but one review 33

Randomized controlled trials

An additional 10 RCTs were located, which were published after the above-mentioned reviews 38-47. For a description of included RCTs please see table 2. Four RCTs included breast cancer patients, another four mixed cancer populations and one lung cancer and prostate cancer, respectively.

Summary of effects by outcome

Effects of MBSR on depression

For breast cancer patients, the meta-analysis Cramer et al. (2012) 33 reported small short-term effects of MBSR compared to usual care on depression. Comparable effects were found in the meta-analysis by Huang et al. (2015) 32, however this analysis used inadequate methods which limit its conclusions. While the meta-analysis by Zainal et al. (2012) 34 found moderate sized effects on depression, the magnitude of effects was reduced when only randomized trials were considered. The most recent meta-analysis by Zhang et al. (2016) 48 finally reported large effect sizes favoring MBSR over usual care.

With regards to the systematic reviews in mixed cancer populations, The meta-analysis by Piet et al. (2012) 35 found small short- and longer-term effects of MBSR on depression for both, innergroup and within-group comparisons. Zhang et al. (2015) 37 found large short-term effects and no medium-term effects favoring MBSR over usual care.

Two of the subsequently published RCTs assessed depression reporting no difference between MBSR and a sleep hygiene intervention 45 or usual care 44.

For a mixed cancer population Piet et al. (2012) 35 reported moderate short- and longer-term effects of MBSR on anxiety when only innergroup comparisons were considered. The effect sizes were small when only randomized trials were considered. In contrast, the more recent review by Zhang et al. (2015) 37 found moderate short-term effects of MBSR on anxiety when compared to usual care, but no medium-term effects.

For anxiety, one of the subsequently published RCTs found effects favoring MBSR over usual care 44, while another did not 46.

Stress was assessed in five of the subsequently published RCTs. Two RCTs reported positive effects of MBSR compared to supportive-expressive therapy 40 or usual care 47, while three found no group differences between MBSR and cognitive therapy 39, a sleep hygiene intervention 45, or usual care (44).

Effects of MBSR on spirituality

The meta-analyses by Cramer et al. (2012) 33 and by Zhang et al. (2016) 48 including breast cancer patients found no effects of MBSR beyond usual care on spirituality.

Effects of MBSR on mindfulness

Based on the review by Piet et al. (2012) 35 including patients with various cancers, MBSR has small short-term effects on mindfulness in both, uncontrolled trails and randomized group comparisons.

The three RCTs published after the systematic reviews report mixed results 45-47.

Effects of MBSR or MBCT on other outcomes

For general distress, only one 47 out of two RCTs found effects of MBSR 47 or MBCT 41 beyond usual care; two studies found no effects of MBSR beyond other psychological interventions 39, 40 reported positive effects of MBSR compared to usual care.

Regarding fatigue, no differences between MBSR and psychoeducation occurred, while MBSR and MBCT were superior to usual care 38, 44.

Health-related quality of lifewas measured in six RCTs; no group differences between MBSR and a sleep hygiene intervention occurred 45; MBSR was superior to usual care in one out of four trials 43, 44, 47; and MBCT was superior to usual care in two trials 38, 41.

Carmody J, Baer RA. How long does a mindfulness-based stress reduction program need to be? A review of class contact hours and effect sizes for psychological distress. Journal of clinical psychology. 2009;65(6):627-38.

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